Don't bother with the Kinetix, get the motordyne or splash out on a Cosworth
Gauges you could run from the TB spacer are nothing worthwhile IMO. The most important gauges you can add will be oil tempurature & AFR IMO (Assumming that you are staying N/A). The ports on the TB spacer will let you run things like a boost gauge, map sensors, FPR etc.
I honestly can't see the TB spacer effecting your fuel consumption at all & definatley not enough to be noticeable